Coil-type continuous flow heater

ABSTRACT

A coil-type continuous flow heater which comprises a combustion chamber, burner means located at one end of the combustion chamber and flue gas outlet means disposed at the other end of said chamber, and pipe coil means substantially lining the combustion chamber, said pipe coil means being coaxially disposed within said chamber so that no gaps exist between the individual coils of said pipe, said pipe coil means also extending a distance from the wall of the combustion chamber so as to define a flue gas duct which is adapted to channel the flue gas from the flue gas outlet means to an outlet means at the burner side of the combustion chamber.

United States Patent 1191 Kiihnlein 11] 3,831,560 1 Aug. 27, 1974COIL-TYPE CONTINUOUS FLOW HEATER [75] Inventor: Hans L. Kiihnlein,Fullinsdorf,

21 1 Appl. No.: 358,999

[30] Foreign Application Priority Data 11/1967 Watson et al l22/2509/1970 Wanson l22/248 Primary Examiner-Kenneth W. Sprague Attorney,Agent, or FirmStewart and Kolasch, Ltd.

[ ABSTRACT A coil-type continuous flow heater which comprises acombustion chamber, burner means locatedat one end of the combustionchamber and flue gas outlet means disposed at the other end of saidchamber, and pipe coil means substantially lining the combustionchamber, said pipe coil means being coaxially disposed within saidchamber so that no gaps exist between the individual coils of said pipe,said pipe coil means also extending a distance from the wall of thecombustion chamber so as to define a flue gas duct which is adapted tochannel the flue gas from the flue gas outlet means to an outlet meansat the burner side of the combustion chamber.

I COIL-TYPE CONTINUOUS FLOW HEATER BACKGROUND AND SUMMARY OF THEINVENTION The present invention relates to a coil-type continuous flowheater containing a burner and used, for example, for heating organicand inorganic heat-transfer agents to a temperature range of about 200to 600C.

Conventional coil heaters which are presently being employed by theindustry for heating no-pressure oils at temperatures of up to about320C. possess the disadvantage that the heat transfer surfaces of thepipe coils are exposed to an uneven load, so that the heattransfer agentis overheated and thus tends to decompose in certain portions of theheat transfer path. This frequently results in a reduction of the flashpoint of the heat-transfer agent which can lead, among other things, toruptures in the pipe coils and attendant leakages therefrom.

In addition, in the heater proper, cracking can also occur wherebydeposits can be formed therein. As a consequence, the pipecoil as aneffective conveying means is destroyed. Thus, a large number of injurieshave been attributed to the above prior art problems found inconventional coil heaters.

Accordingly, it is an object of the present invention to provide aheater of the aforementioned type wherein the heat transfer agent isuniformly heated in all zones of the heat-transfer path and wherein thefilm temperature of the liquid to be heated can be accuratelydetermined.

Other objects and further scope of applicability of the presentinvention will become apparent from the detailed description givenhereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

The coil-type continuous flow heater of the present invention comprisesa heat-transfer path defined by a single pipe coil wound axially andsymmetrically, with the individual pipe windings being in mutual contactwith each other so that no gaps exist between said windings. The pipewindings substantially surround the combustion chamber constituting theradiation zone, except for the mouth of the burner and the flue gasoutlet which are located at opposite ends of the combustion chamber andcoaxially disposed with respect to said chamber and with respect to eachother. The heat transfer path is also encompassed by a flue gas casingwhich forms the convection zone, said flue gas casing being providedwith an outlet at the burner side of the apparatus.

The heat-transfer path which can consist of single or multiple lap pipecoils is suitably constructed as a hollow cylinder with an outwardlyextending conical ceiling and a bottom wall. The heat-transfer agentflows through the pipe coils in the opposite direction to that of theflame in the combustion chamber and in parallel with the flue gasesflowing through the flue gas casing disposed outside of the pipe coil.When the pipe coil contains multiple windings, all of theparallelconnected tubes forming said pipe coil have the same length andthe same flow-through resistance, even if different large flow-throughamounts through the heater are selected. The flue gas casing is suitablysurrounded by an air casing which channels an air-flow therethroughsubstantially parallel to the flow of the flue gases. Because of theoverall arrangement of the elements of the flow heater of the presentinvention, such as for example, the combustion chamber and theheat-transfer path, substantially no heat loss is realized. The filmtemperature of the heat-transfer agent on the coiled pipe wall which isheated on the inside by radiation and on the outside by convectioncan becontrolled at any point of the heater because of the uniform flowthrough all pipe sections. In the case of a multiple-lap pipe coil, theheat absorption is uniform along the flow path in each pipesection.Therefore, an overheating of the system is substantially eliminated,even in the case of an overload or the effect produced by a non-uniformcombustion flame.

BRIEF DESCRIPTION OF THE DRAWING The present invention will become morefully understood from the detailed description hereinbelow and theaccompanying drawing which is given by way of illustration only, andthus is not limitative of the present invention and wherein,

the single FIGURE shows the coil-type continuous flow heater of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION In the drawing, element 1 denotesa pedestal on which is mounted an annular air chamber 2 which isprovided with an inlet pipe 2a. The outer wall of the cylindrical airchamber 2 extends in the upward direction and forms an air channel orcasing; 3 which is provided on the outside with an insulating layer 4which extends down to the pedestal. A flue gas shell 5 is disposed at aradial spacing within the air casing 3 and is in communication at thetop with an annular flue gas trap 6 disposed within the air casing 3.The flue gas trap is provided with an outlet pipe 6a. The air casing 3is closed off at the top by an insulating lid 4a. A burner 7 whichextends through a central aperture :in the lid is provided with adownwardly oriented nozzle 7a which is arranged in the central openingof the flue gas trap 6. The air feeding elements of the burner 7 are incommunication with zones 3a of the air casing 3 disposed above the fluegas trap 6. A multiple-lap pipe coil 8 with mutually contacting pipewindings is radially spaced in the flue gas shell 5. This pipe coilconstitutes the heattransportation path in the heater. This single pipecoil 8, which has a cylindrical main body 8a, contains a top section 8bwhich is conical in shape as it extends in the upward direction and hasa cylindrical collar surrounding the inner wall of the flue gas trap 6encompassing the burner nozzles 7a. The pipe coil 8 also has a bottomsection which is conical in shape as it extends in the downwarddirection and has a central opening 9 axially opposed to the nozzle 7a.This central opening communicates via the distributor channel 10disposed between the bottom section 80 and the air chamber 2, with theflue gas duct 11 which is disposed between the cylindrical section 8aand the flue gas shell .5. Thus the flue gas duct 11 is in communicationwith the trap 6 and the flue gas outlet pipe 60. The interior of thepipe coil 8 disposed between the nozzle 7a and the bottom opening 9fonns the combustion chamber 12 of the heater.

The pipe coil 8, which defines a closed combustion chamber 12 which doesnot contain any gaps, except for the burner mouth and the bottom opening9, is formed by three parallel-connected tubes 13a, 13b and 13c ofequivalent length and substantially identical flow resistance, wound inparallel about the central axis a of the heater. However, the pipe coil8 could also comprise only one winding, that is, consist of only asingle pipe length, or alternatively, it could have more than three pipelengths. ln the zone of the flue gas distributor chamber 10, the threepipe lengths 13a, 13b, and 130 terminate in a collector pipe 14 leadingthrough the air chamber 2 in the downward direction to a heattransferagent inlet pipe 140. The upper ends of the three pipe lengths 13a, 13b,and 13( forming the collar, terminate in a collector pipe 15 disposed inthe flue gas trap 6. This collector pipe extends laterally through thecasings and 3 and the insulating layer 4 to a heattransfer medium outletpipe a.

During the operation of the above-described coiltype continuous flowheater, the heat transfer medium flows from the bottom toward the top inthree equal streams through the pipe lengths 13a, 13b and 13c, andabsorbs heat from the combustion chamber (radiation zone) 12. The hotflue gases pass through the bottom opening 9 into the distributorchamber 10, flow in the upward direction through annular chamber 11 andare conveyed by the trap 6 to the outlet pipe 6a. This conductance ofthe flue gas not only permits an additional heat transfer to the heattransfer medium, but also prevents undesirable high temperaturedifferences between the inner and the outer sides of the pipe coil 8.The identical and equally long pipe lengths 13a, 13b, and 130, all ofwhich are exposed to the same thermal load, that is, on the inside ofthe pipe coil to the radiation zone 12 and on the outside of the pipecoil to the convection zone ll, insure a uniform heating of theheat-transfer medium flowing through each pipe length, in the samequantity, with the same flow through velocity and pressure gradient.

Since the flue gas outlet 9 from the combustion chamber 12 is arelatively narrow, axial opening, the above-described heater could alsobe disposed horizontally instead of vertically, that is, unless theheattransfer medium must be emptied by the force of gravity. Theall-around, no-gap encompassing of the combustion chamber 12 by the pipecoil 8 also insures a uniform exposure of the pipe coil in the radiationzone.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variationsare not to be regarded as adeparture from the spirit and scope of the invention. and all suchmodifications are intended to be included within the scope of thefollowing claims.

It is claimed:

1. A coil-type continuous flow heater which comprises a combustionchamber, burner means located at one end of the combustion chamber andflue gas outlet means disposed at the other end of said chamber, andpipe coil means substantially lining the combustion chamber, said pipecoil means being coaxially disposed within said chamber so that no gapsexist between the individual coils of said pipe, said pipe coil meansalso extending a distance from the wall of the combustion chamber so asto define a flue gas duct which is adapted to channel the flue gas fromthe flue gas outlet means to an outlet means at the burner side of thecombustion chamber, said pipe coil means further comprising multiplewindings having substantially equal lengths and flow resistances, saidmultiple windings being connected in parallel and emanating from aninlet collector tube disposed at the flue gas outlet end portion of thecombustion chamber and terminating in an outlet collector tube which isdisposed at the burner end of the combustion chamber and a flue gas trapdisposed at the burner end portion of the combustion chamber and a fluegas distributor chamber disposed at the other end portion of thecombustion chamber, said flue gas duct communicating at the burner endportion of the combustion chamber with said flue gas trap and with theflue gas distributor chamber at the other end portion of said combustionchamber.

2. The coil type continuous flow heater of claim 1, wherein the pipecoil means has a cylindrical main body and conical end portions, one ofsaid end portions being adapted to receive the nozzle of the burnermeans and the other of said end portions containing the flue gas outletmeans.

3. The coil type continuous flow heater of claim 2, wherein the pipecoil means forms a collar which surrounds the nozzle of the burnermeans.

4. The coil type continuous flow heater of claim 1, wherein an aircasing is disposed between the flue gas duct and the wall of thecombustion chamber, said air casing provided at one end portion of thecombustion chamber with air inlet means and terminating at the burnerend portion of the combustion chamber in an air chamber whichcommunicates with the air feeding elements of the burner.

5. The coil type continuous flow heater of claim 1, wherein the pipecoil is vertically disposed within the combustion chamber.

6. The coil type continuous flow heater of claim 1, wherein the pipecoil is horizontally disposed within the combustion chamber.

1. A coil-type continuous flow heater which comprises a combustionchamber, burner means located at one end of the combustion chamber andflue gas outlet means disposed at the other end of said chamber, andpipe coil means substantially lining the combustion chamber, said pipecoil means being coaxially disposed within said chamber so that no gapsexist between the individual coils of said pipe, said pipe coil meansalso extending a distance from the wall of the combustion chamber so asto define a flue gas duct which is adapted to channel the flue gas fromthe flue gas outlet means to an outlet means at the burner side of thecombustion chamber, said pipe coil means further comprising multiplewindings having substantially equal lengths and flow resistances, saidmultiple windings being connected in parallel and emanating from aninlet collector tube disposed at the flue gas outlet end portion of thecombustion chamber and terminating in an outlet collector tube which isdisposed at the burner end of the combustion chamber and a flue gas trapdisposed at the burner end portion of the combustiOn chamber and a fluegas distributor chamber disposed at the other end portion of thecombustion chamber, said flue gas duct communicating at the burner endportion of the combustion chamber with said flue gas trap and with theflue gas distributor chamber at the other end portion of said combustionchamber.
 2. The coil type continuous flow heater of claim 1, wherein thepipe coil means has a cylindrical main body and conical end portions,one of said end portions being adapted to receive the nozzle of theburner means and the other of said end portions containing the flue gasoutlet means.
 3. The coil type continuous flow heater of claim 2,wherein the pipe coil means forms a collar which surrounds the nozzle ofthe burner means.
 4. The coil type continuous flow heater of claim 1,wherein an air casing is disposed between the flue gas duct and the wallof the combustion chamber, said air casing provided at one end portionof the combustion chamber with air inlet means and terminating at theburner end portion of the combustion chamber in an air chamber whichcommunicates with the air feeding elements of the burner.
 5. The coiltype continuous flow heater of claim 1, wherein the pipe coil isvertically disposed within the combustion chamber.
 6. The coil typecontinuous flow heater of claim 1, wherein the pipe coil is horizontallydisposed within the combustion chamber.